Common Registration Assessment, Part 1

Desogestrel 75 microgram tablets and the missed pill window for the GPhC assessment

Three original practice questions, with the working shown. Read the stated prescription or plan before calculating.

Published 14 November 2026. Independent revision material, not GPhC questions, not for patient care.

Hands holding a plain blister pack of tablets and a glass of water
Photo from Pexels, used under the Pexels licence. It is a stock image and does not show the exercise.

The manufacturer's UK product information for Cerazette (desogestrel 75 micrograms) gives one tablet every day at about the same time, taken continuously with no break between packs.

Contraceptive protection may be reduced if more than 36 hours have elapsed between two tablets, which leaves a 12-hour window around the usual tablet time.

For a tablet taken less than 12 hours late, the product information says to take it as soon as it is remembered and take the next tablet at the usual time. For a tablet more than 12 hours late, an additional method of contraception is needed for the next 7 days.

Each question fixes the values needed for its arithmetic. Count the hours from the usual tablet time and state the window beside every answer. All prescriptions and patients here are fictional; these are revision materials, not for patient care.

The method

  1. Take one tablet daily at about the same time, with no break between packs.
  2. Measure lateness in hours from the usual tablet time.
  3. Under 12 hours late: take the missed tablet as soon as it is remembered and the next at the usual time.
  4. More than 12 hours late: take the missed tablet as soon as it is remembered and use an additional method of contraception for the next 7 days.
  5. Keep the 36-hour figure in mind as the outer limit between two tablets.

Three practice questions

Work each one on paper first, then open the answer. All patients and prescriptions are fictional.

Question 1

A fictional patient usually takes a tablet at 21:00 and remembers the next morning at 06:00. Is protection maintained, and what should she do?

Show the answer

Answer: Yes; 9 hours late is within 12 hours, so she takes the tablet as soon as remembered and the next at the usual time

Working: 21:00 to 06:00 is 9 hours, which is less than 12 hours late, so the product information says to take the missed tablet as soon as it is remembered and take the next tablet at the usual time.

Question 2

A fictional patient usually takes a tablet at 08:00 and remembers at 22:00 the same day. What does the product information advise?

Show the answer

Answer: Take the missed tablet as soon as remembered and use an additional method of contraception for the next 7 days

Working: 08:00 to 22:00 is 14 hours, which is more than 12 hours late, so the product information adds an additional method of contraception for the next 7 days.

Question 3

A fictional patient last took a tablet 40 hours ago. What does the 36-hour figure in the product information say about protection?

Show the answer

Answer: Protection may be reduced, because more than 36 hours have elapsed between two tablets

Working: 40 hours is greater than 36 hours. The product information states that contraceptive protection may be reduced if more than 36 hours have elapsed between two tablets.

eMC SmPC: Cerazette 75 microgram film-coated tablets

https://www.medicines.org.uk/emc/product/1698/smpc

Where marks are lost

  • Leaving a tablet-free break between packs when the product information gives continuous daily taking.
  • Counting lateness from midnight or from waking instead of from the usual tablet time.
  • Treating a tablet taken more than 12 hours late like one taken within 12 hours and skipping the 7 days of additional contraception.

Frequently asked questions

Are these official assessment questions?

No. They are original revision exercises, not official GPhC questions and not for patient care.

Does this calculation decide a real dose?

No. Follow the stated prescription in the exercise. Real dosing follows the prescriber and the product information for the named product.

How should I check the answer?

Measure the hours from the usual tablet time to the remembered time, compare with 12 hours, then apply the matching rule in the product information.

Sources

The questions above are original and use fictional patients and prescriptions. PreRegExamPrep is not affiliated with or endorsed by the General Pharmaceutical Council.

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More calculation topics

See also the formula sheet, the eight sample questions and the approved calculator page.